The protection of Indian water rights, in particular tribal rights to groundwater, has taken on increased urgency as the American West enters successive years of drought in what appears to be a trend towards long-term climate change with its broader implications. As states struggle to control and conserve their reserves of groundwater from depletion in drought conditions, tribal rights to groundwater are moving to the forefront of efforts to protect Indian water rights. California, which is experiencing "exceptional drought" conditions in most areas of the state, is the last of the western states to pass legislation regulating groundwater. In California's arid environment, with its multiple and diverse demands by multiple private and municipal water users, the potential threat to tribal groundwater rights cannot be ignored. The urgency of the situation is compounded by an increasing state population and the resulting expansion in recent decades of urban areas to the edges of Indian reservations, with accelerated demands being placed on local and shared groundwater sources. In this water-scarce and high-demand environment, protection of essential and valuable tribal rights to groundwater cannot be assured without confirming the actual extent of the tribal water right through quantification or other means. The specific concerns raised in this article are not unique to California; however, California provides an extreme example because of the current drought and the large clusters of Indian reservations in Southern California dependent on groundwater for their sole or primary source of water.

Just as in situations of off-reservation diversion of surface waters that are sources of tribal water rights, off-reservation pumping and recharge of groundwater from basins underlying or adjacent to reservations can threaten the continued, sustained yield of these water sources to satisfy the purposes of the reservation. It is the intent of this article to focus on the development of strategic approaches to preserve the exercise of tribal rights to groundwater and to protect tribal access to usable groundwater under federal and state law in the absence of, and as an alternative to, a general stream or basin adjudication.

A preliminary step towards that protection is to determine the extent of a tribe's groundwater rights. In California, most of the Indian water rights, including rights to groundwater, remain unquantified. Until these rights are quantified, they remain vulnerable to the competing water needs of local governments and private entities. Unless tribes assess for themselves their current and potential future demand for water and determine how this demand correlates to their rights to water under federal and state laws, their ability to protect these rights from encroachment by other water users will be severely compromised. This is especially so in a state like California that does not regulate groundwater pumping and in which groundwater supplies over half of the water in dry years. The development of effective strategies for the protection of tribal rights to groundwater, therefore, will involve the investigation and quantification of tribal water rights through comprehensive studies. It will also involve the development of tribal groundwater management plans and water codes and an understanding of the mechanisms available under state law to protect these rights.

These efforts must consider the interplay between federal and state water law governing tribal rights to groundwater, the role of evolving state water policy, the ways tribes can use their own authority to manage and protect groundwater resources, and the relationships between tribes and competing water users. Within the broader discussion of strategies are the tribes' ongoing efforts to confirm their federally reserved water rights through litigation or settlement, and to protect the quality of their water by applying federal law, establishing tribal groundwater management plans, using state law protections, and enacting tribal ordinances. Furthermore, notwithstanding the protections afforded by state common law to certain rights to groundwater, these protections are not part of a regulatory regime and do not have the broad scope that are part of the federally reserved water right in terms of priority date, purposes, and the inclusion of both present and future uses consistent with the purposes of the reservation.

Finally, there is an overriding factor that will play an increasing role in the groundwater discussion, and that is the specter of climate change with its long-term implications for tribal water supply and water quality - in other words, "scarcity," and in some cases "extreme scarcity." Though it is beyond the scope of this article to delve into its effects, climate change implicates an increasingly competitive, water-scarce environment in which it is urgent to secure tribal groundwater rights and protect groundwater sources serving tribes.